i have a 90g.once full of rock,sand,water and all the other stuff it weights approx 900 lbs.900lbs will be spread over the entire surface area of the base of the stand.the stand has 6 sq feet of surface area.900 divided by 6=150.so in theory you should have approx 150/sq foot exerted on your floor.shouldnt be a problem.if you are worried try to get a copy of the house plans and find out floor joist placement.also you could contact the builder and ask if its a problem but id imagine they build the house to hold a waterbed.